The present invention relates to a communication proxy apparatus, which relays communication between a server device and a client device as an agent in a network system including WWW (World Wide Web) used for accessing information data on the server device from the client device connected through a communication line, and also relates to a system that uses said communication proxy apparatus.
A conventional communication proxy technology is described in RFC2068 “Hypertext Transfer Protocol—HTTP/1.1” (pages from 11 to 13) issued on January 1997. According to this prior art, a communication proxy apparatus for relaying communication as an agent is provided between a WWW server device and a client device to speed up an access to World Wide Web data, which is information data on the server device, from the client device.
In the prior art, speed-up of an access from the client device is achieved by the following: the communication proxy apparatus for relaying communication between both devices as an agent is provided between the server device and the client device; and the communication proxy apparatus maintains and manages relayed information data as a cache. More specifically, the congestion of accesses from the plurality of client devices to the server device are prevented, and speed-up of an access from each client device is achieved, by the following steps: holding information data, which has been relayed by the communication proxy apparatus as an agent, as a cache; and for an access request from the client device for an access to information data, of which a latest version has already been held as a cache, not relaying the access request as an agent, but returning the cache.
In addition, a technology for efficiently accessing information data on a server device, which is periodically updated, from a client device is described in “An introduction to XML” issued by Nihon Keizai Shimbun, Inc. in 1998 (pages from 36 to 47).
In this prior art, cache expiration time information is added to information data, which is distributed from the server device, as attribute information of the information data, before transmitting the information data to client devices. Client devices can acquire the latest information data by reacquiring the latest information data repeatedly according to the cache expiration time information.